内耳圧変動に関する実験的研究

抄録

The intralabyrinthine pressure of the curarized guinea-pig was measured by use of electromanometer of a high sensitivity wire resistance strain gauge type.
By the present experimental procedures, the fine changes of the intralabyrinthine pressure could be thoroughly observed.
Method and experimental procedure;
Guinea-pigs weighning 400-600g were used. The intralabyrinthine pressure changes were recorded by means of a steel pipette mounted on a micromanipulator. The pipette was made from steel tube, its external diameter was about 300μ, and internal diameter of its orifice about 100μ. The pipette was connected with a pressure transducer (strain gauge type, TMI model LPU-0.5) by the aid of the polyethylene tube, the above system were filled with a high-potassium and low-sodium isotonic solution according to C. A. Smith's report.
The animal was anaesthetized intraperitoneally with pentobarbital sodium and was given tubocurarine chloride intravenously. Then, the animal was survived by artificial respiration. The cochlea was exposed through the auditory bulla by a submandibular approach. With the aid of a binocular dissecting microscope, a small hole of about 100μ in diameter was made at the stria vascularis area in the basal turn of the cochlea for the measurement of the endolymphatic pressure. For measuring the pressure of the perilymph, the fenestra was made just below the stria area.
Above procedures were carried out carefully avoiding piercing the soft tissue of the stria vascularis and escape of the intralabyrinthine fluids. Then, the pipette with a drop in its tip was driven with the aid of a micromanipulator to the fenestra, coming in close contact with the fenestra. At this point, the stria was not yet penetrated and all of recording system was still opened to the atmosphere. After the zero point of the pressure was calibrated, again the pipette was advanced in the cochlea.
Immediately after the penetration with the pipette to the cochlear wall, the intralabyrin- thine pressure of 30-70 mmH₂O height was recorded, and then the changes of the pressure could be recorded continuously.
Results;
1) The static pressure of endolymph was about 47 mmH₂O high, and about 50 mmH₂O high in the perilymph (Scala tympani). However, from the histological observation of the cochlea of the guinea-pig, some doubts were raised in measuring method of the endolymphatic pressure.
2) Under normal conditions (not anaesthetized), the intralabyrinthine pressure was not stable, but always changing under the influence of many factors; such as breathing movement, contraction of the tympanic muscles and cerebrospinal pressure changes.
3) Anoxia (asphyxic asphyxia) caused a marked increase in the pressure. The first increase was observed at the beginning of the anoxia, and maintained constant height till the cessation of the anoxia.
The second increase was observed after cessation of the anoxia. In parallel with these increase in the pressure, the pulse wave of the inner ear blood vessels increased its amplitude. This pulse wave was observed as the changes of the intralabyrinthine pressure.
4) Intravenous injection of vasodilator such as papaverine, caused a transient increase in the pressure and the amplitude of the pulse wave.
5) Intravenous injection of adrenaline and nor-adrenaline caused immediate increase in the pressure. Following this increase, a decrease in the pressure continued for several minutes.
6) Intravenous injection of hypertonic solutions such as 20% mannitol, 30% urea, caused gradual decrease in the pressure, and then showed gradual increase. These changes continued for several hours.
7) Occasionally a transient increase in the pressure was measured after intense sound stimulation.
8) Bleeding from carotid artery caused a marked decrease in the pressure.